A suction muffler of this kind is known from DE 36 45 083 C2. It is particularly applied in connection with small, enclosed refrigerating machines, as used in the domestic area for refrigerators and freezers. The refrigerant gas sucked in through the suction muffler always contains an amount of oil, part of which precipitates inside the muffler. This oil gathers in the chamber. At the bottom of the chamber an oil discharge opening is provided, through which the precipitated oil can run out of the chamber. However, this oil discharge opening can also create an acoustic coupling between the chamber and the environment of the suction muffler. In the known case, a tube is provided, which is connected to the oil discharge opening. This tube can be dimensioned so that an acoustic coupling is created, which ensures a sufficient suppression of the interfering frequencies. Depending on the pressures during operation, more or less oil will gather in the tube, sticking to its walls.
In such suction mufflers, the problem is that the oil from the refrigerant flow settling in the chamber cannot immediately flow to the oil sump during operation of the compressor. Exceptions occur when, for example, the inlet opening is arranged at the deepest spot of the chamber, which, however, cannot usually be assumed. Particularly critical is the situation, when the refrigerant is led direct from the inlet pipe connector of a compressor housing to the suction muffler, as in this case much oil is contained in the refrigerant flow. As long as the compressor of the refrigerating machine is in operation, the pressure inside the chamber is somewhat lower than that outside the housing, as refrigerant gas is currently sucked off from the chamber. This pressure difference naturally also acts upon the oil outlet opening, that is, counteracts the discharge of the oil from the chamber. Not until the compressor is disconnected, is the pressure equalised, thereby allowing the oil gathered in the chamber can flow off at the bottom by means of gravity. With a long and uninterrupted operation period, a considerable amount of oil can gather in the chamber, which causes several disadvantages. Firstly, oil, which is required for lubrication and cooling, is taken away from the compressor. Secondly, the volume of the chamber available for muffling is reduced. Most important, however, is that the more oil is gathered in the chamber, the larger is the amount of oil, which is carried along by the refrigerant, the so-called external oil circulation. This oil in the refrigerant circuit is undesirable, as the oil will reduce the heat transfer in the heat exchangers of the circuit. When too much oil is contained in the refrigerant flow, the risk of a fluid stroke in the compressor exists, when too much oil is sucked into the cylinder of the compressor.
The invention is based on the task of avoiding the situation where too much oil remains in the chamber.